Electronic Brake Force Distribution

What is Electronic Brake Force Distribution (EBD)?

skidding car without ebd
EBD brakes can prevent tires from locking up, which can help avoid dangerous skidding like this.  Warwick Kent / Photolibrary / Getty

Electronic brakeforce distribution (EBD) is a system of additional brake controls that can augment, and improve the functionality of, anti-lock brakes.

This is typically accomplished by monitoring a number of different systems and sensors and varying the amount of force applied to each individual brake caliper. By modulating the amount of brakeforce that is applied, based on road and driving conditions, EBD brakes can help prevent dangerous skids.

How Does Electronic Brake Force Distribution Work?

Since most original equipment manufacturers (OEMs) offer at least one model with EBD, there are a lot of different kinds of EBD brakes that you can run into.

However, EBD systems typically make use of components like:

  • speed sensors
  • brake force modulators
  • electronic control units
  • yaw sensors
  • steering wheel angle sensors

Many of these components are also used by other brake-related systems, like electronic stability control and traction control.

The way that EBD brakes typically work is that the system looks at data from speed sensors to determine if any of the wheels aren't rotating at the same speed as the others. If a discrepancy is found, indicating that a tire may be skidding, corrective measures can be taken.

These systems can also compare the data from a yaw sensor to the data from a steering wheel angle sensor to see if the vehicle is over- or understeering. That data is then processed by the electronic control unit to ascertain the relative load on each wheel.

If the electronic control unit determines that that one or more wheels is under a lighter load than the others, it is capable of using brake force modulators to reduce the brake force to that wheel. This occurs dynamically, so the brake force can be modulated continuously in response to the prevailing conditions.

What’s the Point of Electronic Brake Force Distribution?

The purpose of EBD is similar to the purposes of related technologies like anti-lock brakes and traction control. These technologies are all designed to prevent the wheels of a vehicle from locking up, which can cause a driver to lose control very quickly. Unlike other brake systems, EBD is able to dynamically modulate the brake force that’s applied to each wheel.

The general idea behind electronic brake force distribution is that wheels lock up more easily when they are under a light load. Traditional proportioning valves deal with this issue by applying different brake force levels to the front and rear wheels, but these hydraulic valves aren't capable of reacting to different circumstances and conditions.

Under normal circumstances, the weight of a vehicle will shift forward as it slows down. Since that puts a heavier load on the front wheels than the rear ones, EBD systems can respond to that situation by decreasing the brake force on the rear wheels. However, a vehicle that is heavily loaded in the rear will behave differently. If the trunk is full of luggage, an EBD system is capable of sensing that increased load and modulating the brake force accordingly.

What’s the Best Way to Drive a Vehicle That has Electronic Brake Force Distribution?

If you find yourself in a vehicle that includes EBD, you should drive it like any other vehicle that has anti-lock brakes.

These systems work behind the scenes to automatically adjust for extra weight in the trunk, icy or wet conditions, and other variables, so no extra effort is needed on your part. However, it is a good idea to be extra careful when braking and cornering until you’re familiar with the way that the vehicle handles.

What Happens When Electronic Brake Force Distribution Fails?

In the event of EBD failure, the conventional brake system should continue to function normally. That means you’ll typically be fine if you have to drive a vehicle that has a malfunctioning EBD system. However, you’ll need to take extra care when braking.

Since EBD and ABS use many of the same components, your anti-lock brakes will often fail at the same time as your electronic brake force distribution system, which means you may need to pump your brakes instead of applying steady pressure.

Some manufacturers recommend that you check your brake fluid level if you suspect a malfunctioning EBD system, since some vehicles use the same warning light for low fluid that is used for other brake issues. If the fluid level is low, you should avoid driving the vehicle until it has been topped off, and a mechanic should inspect the system for leaks.